header {
  position: fixed;
  width: 100%;
  top: 0;
  box-shadow: 0 0 1px rgba(0, 0, 0, 0.25);
  transition: background-color 0.3s ease-in-out;
  background-color: #fff;
  height: 60px;
  padding: 10px 60px;
  z-index: 2;
}

.po_banner {
  background: url(../../images/banner1.jpg) no-repeat top center;
  max-width: 1920px;
  height: 276px;
  overflow: hidden;
  width: 100%;
}

main {
  margin-top: 60px;
  width: 100%;
}

nav {
  list-style-type: none;
  line-height: 40px;
  position: fixed;
  right: 30px;
  top: 10px;
  height: 60px;
}

nav li {
  position: relative;
  margin: 0 1.5em;
}

.nav-link {
  font-size: 22px;
  padding-bottom: 3px;
  white-space: nowrap;
  cursor: pointer;
}

.nav-link:hover,
.nav-link.current {
  border-bottom: 3px solid #42b983;
}
